Alkylation and catalyst recovery



Patented Feb. 22, 1949 ALKYLATION AND CATALYST RECOVERY Robert J. Lee,La Marque, Tex., assignor to Pan American Befinln g Corporation, NewYork,

N. Y., a corporation of Delaware No Drawing. Application August 9, 1945Serial No. 609,941

, 8 Claims. 7 1

This invention relates to an alkylation process. More particularly, itrelates to an alkylation process wherein an aromatic sulfonic acidcatalyst is employed. In a preferred form, this invention relates to thealkylation of an alkylatable hydrocarbon with an oleflnic hydrocarbon inthe presence of a substantially anhydrous toluene sulfonic acid.

hydrocarbon employing an olefin as an alkylating agent and an aromaticsulfonic acid catalyst, the alkylation reaction mixture is worked up bytreatment with an aqueous or alcoholic alkali, e. g., NaOH, to removefree aromatic sulfonic acids and the alkali-treated reaction mixture isthen subjected to fractional distillation to separate prod- 'ucts andunreacted materials. Catalyst losses,

for a reason not hitherto appreciated, were excessive, and theemployment of aromatic sulfonic acids was not considered practicalexcept for the alkylation of small amounts of diflicultly alkylatablecompounds such as certain nitrogen-containing organic compounds having avery high market value.- In the fractional distillation equipmentemployed in these processes, excessive corrosion has been encounteredand, at times, plugging of the condensers, run-down lines and the like.Thus, in processes wherein anhydrous toluene sulfonic acid catalysts areemployed for alkylation of aromatics with olefins, excessive catalystlosses, corrosion of distillation equipment and plugging of condenserlines resulted upon working up the reaction mixture in the mannerdescribed above.

It is an object of this invention to provide an improved process for thealkylation of alkylatable hydrocarbons wherein aromatic sulfonic acidcatalysts are employed. Another object of this invention is to providean improved process for the alkylation of aromatic hydrocarbons withsubstantially anhydrous toluene sulionic acid catalysts whereinover-alkylation of the aromatic hydrocarbon is substantially avoided. Anadditional object is to provide an improved continuous alkylationprocess wherein aromatic suifonic acid catalysts are employed. Stillanother object of this invention is to provide an improved method ofworking up the alkylation products and recovering and re-using catalystin alkylation processes employing aromatic sulfonic acids as catalysts.A further object of this invention is to prevent plugging of condenserson product fractionators used in processes wherein alkylatablehydrocarbons are alkylated with oleflns in the presence of aromaticsulfonic acids. Still other objects will become apparent from thefollowing description of this invention.

In accordance with this invention, the aboveenumerated difiicultiesencountered in alkylation processes employing substantially anhydrousaromatic sulfonic acid catalysts can be obviated by subjecting thealkylation reaction mixture, after discontinuing the injection of olefinhydrocarbons into said reaction mixture, to a suitable tempera- Inprocesses for the alkylation of an alkylatable ture for a period of timesuflicient to result in substantial regeneration of free aromaticsulfonic acids from aromatic sulfonic esters which are formed in thecourse of the alkylation operations.

\ The treatment of aromatic sulfonic esters to produce free aromaticsulfonic acids will hereinafter be described as aromatic sulfonic esterconversion. The regenerated aromatic sulfonic acids can then be readilyremoved from the alkylation products, e. g., by washing with an alkalinematerial such as caustic. After the regeneration and removal of aromaticsulfonic acid, the alkylation products may be readily distilled orfractionated without encountering excessive corrosion in thedistillation equipment or plugging or fouling of condensers used inconjunction with the distillation equipment. The sulfonic acid catalystmay be regenerated from the alkali washing liquor and may be recycled tothe alkylation reactor after a dehydration treatment. The process of thepresent invention renders possible substantially complete catalystrecovery for re-use in alkylation.

Other methods of separating regenerated aromatic sulfonic acids from thereaction mixture can also be used. A particularly desirable method ofseparation comprises diluting the alkylation reaction mixture with asaturated aliphatic hydro? sulfonic acid in the alkylation reactionmixture,

'thereby yielding a distinct stratum of aromatic sulfonic acid which canbe separated from the alkylation products and re-used. Ordinarily, theaddition of about 0.25 to about 3 volumes of saturated aliphatichydrocarbon such as hexanes, cyclohexane, pentanes, butanes, or theirhomologs or mixtures, e. g., naphtha, kerosene, gas oil, or the like,per volume of the alkylation reaction mixtur is suflicient, although itwill be understood that in some instances even greater dilution of thealkylation reaction mixture may be necessary. Temperatures between about50 and about F. may

be conveniently maintained during the separation of the aromaticsulionic acid phase from the alkylation products phase. The smallproportion, e.g., 1-3%, of regenerated aromatic sulfonic acid whichremains in solution in the alkylate can be removed by washing with wateror alkalies 'prior to fractionating the alkylate.

This inventionis particularly applicable to con tinuous alkylationprocesses. In a continuous process, an aliquot portion of the alkylatereaction mixture is removed continuously or intermittently and treatedin accordance with the process of the invention to recover aromaticsulfonic acid catalyst, which is preferably recycled to the alkylationreactor, and alkylation products which are fractionally distilled torecover desired alkylates and unalkylated and/or over-alkylatedmaterials, which may also be recycled to the alkylation reactor.

In order to prevent alkylation of the alkylatable hydrocarbon feed stockbeyond the desired exalkyla'table substance, which is not identical withthe feed stock used in the alkylation process. In a desirablealkylation' process, olefinic hydrocarbons are injected into analkylation reactor containing the alkylatable hydrocarbon and aromaticsulfonic acid catalyst until the alkylatable hydrocarbon has beenalkylated to the desired extent, the olefin injection is discontinued,an alkylatable substance is thereafter added to the alkyla on reactorand the aromatic sulfonic ester formed during the course of thealkylation operation is converted to aromatic sulfonic acid and analkylated substance. Alkylatable substances suitable i'or use in ourprocess include phenols, aromatic hydrocarbons, various sulfur andnitrogen compounds containing hydrogen bonded thereto, etc

The process of this invention can be practiced with a wide variety ofalkylatable hydrocarbons.

aromatic hydrocarbons, e. g., benzene, toluene,

. xylenes, ethylbenzene, ethyltoluenes, cymene,

cumene, n-propyl benzene, isopropyl benzene, naphthalene and alkylnaphthalenes, e. g., methyl naphthalenes, dimethyl naphthalenes, andtrimethyl naphthalenes, diphenyl, alkyl diphenyls,

'anthracene, alkyl anthracenes, phenanthrenes,

forming) and other processes which produce aromatic hydrocarbons.

Specifically, the process of this invention has been applied withgratifying results to synthetic aromatic hydrocarbon fractionscontaining a high proportion of alkyl polycyclic aromatic hydrocarbons,particularly mono-, di-, and trimethyl naphthalenes. Suitable sources ofalkyl polycyclic aromatic hydrocarbons for use in our process aresynthetic hydrocarbon fractions obtained by the catalytic conversion ofpetroleum oils with catalysts comprising at least one metal oxideselected from groups 2 to 6, inclusive, of the periodic table.

A suitable process for the production of alkyl polycyclic aromatichydrocarbons is the hydroforming process. In this process a petroleumnaphtha, which may be a virgin or cracked naphtha or mixture of both, isconverted to aromatic hydrocarbons by contact with a solid, porousdehydrogenation catalyst at a temperature in the range of about 850 F.to about 1050 F., preferably in the presence of hydrogen. Suitablecatalysts are oxides of metals of groups 2 to 6 of the periodic system,particularly oxides of 6th group metals such as chromium and molybdenum,preferably supported by alumina or magnesia. Excellent catalysts can beprepared by depositing about 4 to about of molybdenum oxide upon anactivated alumina. Suitable space velocities for hydroforming fallwithin the range of about 0.2 to about 4 volumes of the liquid chargestock per hour per volume of catalyst space. About 0.5 to about 8 molsof hydrogen can be charged to the process with each mol of naphtha feedstock. In addition to a high octane number naphtha, the hydroformingprocess produces a. fraction which boils above the naphtha range, forexample, in the range of about 425 to about 650 F., which isknown ashydroformer bottoms.

Hydroformer bottoms comprises a complex mixture of alkyland polyalkylpolycyclic aromatic hydrocarbons, including relatively large.proportions of monoand polymethyl naphthalenes.

The process of this invention can also be ap-.

. plied to alkyl polycyclic aromatic hydrocarbons It is preferredparticularly for the alkylation of derived from certain crude petroleumoils by extraction with selective solvents. Alkyl polycyclic aromatichydrocarbons are also present to a considerable extent in cracked cyclestock produced by cracking high boiling petroleum oils such. as gasoils, preferably with catalysts. Cracking with solid cracking catalystsc0mprising one or more oxides of metals selected from groups 2 to 6,inclusive, of the periodic table can be effected at temperatures of theorder of about 850 to 1050 F. and pressures of atmospheric to 50 p. s.i. or even higher. A suitable cracking catalyst is active silicapromoted with about 5 to about of active alumina or magnesia. Also,activated clays can be used as catalysts. Alkyl polycyclic aromatichydrocarbons can be concentrated from cracked cycle stocks by a varietyof selective solvents. Suitable selective solvents include nitromethane,nitroethane, ethylene glycol monoethyl ether, diethylene glycolmonoethyl ether, diethylene triamine, dipropylene glycol, methanol,ethylene glycol monomethyl ether,

diethylene glycol monomethyl ether, morpholine ethanol,

triethylene tetramine, tetraethylene pentamine, etc.

A wide variety of olefinic hydrocarbons can be used as alkylating agentsin our process, e. g., propylene, butene-l, butene-2, isobutene,pentenes, hexenes, heptenes, and the like.

Aromatic hydrocarbons can generally be a1- kylated by oleflnichydrocarbons in the presence of aromatic sulfonic acid catalysts attemperatures in the range of about 150 to about 400 F., providing thatthe highest temperature chosen for alkylation does not exceed thedecomposition temperature of the particular sulfonic acid used as thecatalyst. With substantially anhydrous toluene sulfonic acids,alkylation temperatures in the range of about 265 to about 300 F.

are preferred. Alkylation pressures may be atmospheric or higher, e. g.,0 to p. s. i. g. or even higher. The proportion of aromatic sulfonicacid catalyst may vary from about 1 to about 20 mol percent based on thearomatic hydrocarbon feed stock, or even more, the upper limit being insome instances, determined by the limiting solubility of the catalyst inthe aromatic hydrocarbon feed stock. Ordinarily, increased rates ofalkylation are obtained with increasing amounts of catalyst in thereactor. The specific f eed stocks, catalysts, proportions of catalysts,and desired extent of alkylation will, naturally, affect the optimumduration of the reaction period. Normally, for mono-alkylation, reactionperiods in the range of about 5 to about 25 hours may be used.

The specific aromatic sulfonic ester conversion temperatures employed inthe process of this invention will depend upon the particular aromaticsulfonic ester formed in the process. In general, conversion of theester may be effected at the temperatures used in the alkylationprocess. The rate of conversion may be increased by operating at atemperature above the alkylation temperature but not in excess of thedecomposition temperature ofthe corresponding aromatic sulfonic acidand/or under a pressure below that employed in the alkylation operation,particularly atmospheric or lower pressures such as pressures of 100,25, 10, or even 1 mm. of mercury. Generally suitable aromatic sulfonicester conversion temperatures fall within the range of about 150 toabout 400 F. Suitable conversion temperatures for toluene sulfonicesters will generally fall within the range of about 200 to about 300 F.The time necessary to effect conversion will depend on the particulararomatic sulionic ester, its amount, other conversion conditions, thedesired extent of conversion, etc. Suitable times corresponding with thegeneral conversion temperature range given above ordinarily exceed about0.5 hour, and may fall within the range of about 1 to about hours. Withanhydrous toluene sulfonic esters, conversion times in excess of about0.5 hour may be used, preferably about 2 to about 4 hours. It may bepossible to increase the rate of conversion by the use of catalysts,such as hydrogen chloride gas, hydrogen fluoride, active clays, BFs,etc.

During conversion of the aromatic sulfonic ester it is desirable tosubject the mixture of alkylation reaction products to vigorousagitation. Mechanical agitation may be used alone, or may besupplemented with or supplanted by agitation with gases which serve alsoas a stripping medium. A refinery propane or butane stream may, forexample, be used as a stripping and agitating gas.

The following examples are illustrative, but not limitative of myinvention. The aromatic hydrocarbons to be alkylated were alkylnaphthalenes obtained from hydroiormer bottoms. The examples describethe use of my preferred catalyst, a substantially anhydrous toluenesulfonic acid. The catalyst may be ortho-, meta-, or paratoluenesulfonic acid, but I prefer to use a technical" toluene sulionic acidwhich contains more than one isomer and may contain all three.

I have found that the substantially anhydrous toluene sulionic acids aremuch more soluble in hydrocarbons than hydrous toluene sulfonic acidsand can be used as homogeneous catalysts under conditions where hydroustoluene sulfonic acids are, quite immiscible with hydrocarbon feedstocks. Furthermore, anhydrous toluene sulfonic acids appear to inducehigher reaction rates than the hydrated acids. In fact, in manyinstances. hydrated toluene sulfonic acid has been found to besubstantially devoid of catalytic alkylation activity. Typical toluenesulfonic acids which I have employed as catalysts for the alkyl-ation ofalkyl polycyclic aromatic hydrocarbon with olefins have the followingproperties:

TABLE I Neutralization equiv. (theory: 172) 177.5

Density, grams/ml. at 84.9 F l.

Refractive index:

(a) Of 11.4% aqueous solution 1.352 (0) Calculated to 100% toluenesulfonic acid 1.507 Crystallizing point, F. (approx.) Water content,weight, percent (by reflux- 1.05

ing with toluene, 3.5 hours) Physical appearance Viscous liquid orsemicrystalline mas de pending on temperature; dark reddish brown color.

Assay (toluene sulionic acids) 94.0% (min.)

Free 112804.. 1.0% max.)

Toluene 0.2% max.)

Water" 2.0% (man;

Suliones 3.0% max.

Para toluene sulfonic acid 823g, (approx.)

Ortho toluene sulfonic acid 0 (approx.)

Table II sets forth examples of the butylation and propylation ofhydroformer bottoms fractions. In Table II, the hydroformer bottomsfraction boiling in the range of 437 to 554 F. comprised predominantly amixture of mono-, di-, and trimethyl naphthalenes. The hydroformerbottoms fraction boiling at 482 to 527 F. comprised predominantlydimethyl naphthalenes. Specific operating procedures used in obtainingthe data set forth in Table II will be described below.

TABLE 11 Preparation and properties of bulylaied and prppylaied alkulnaphthalene-9 Pxamnla 1 2 3 52032 151010;): aglid dlbutyl grade 11101,};and dibutyl. gifiigopyll.

i r as n e Alkylation Conditions: 5 gano S er g ass M01 per cent.toluene sulfonic acid 3 10 8. P catalyst. ressure At 30 g emperaturefllassp s l g i i me 80hrs 18hrs 92 inc cess Mglstolle fln absorbed/moihydroiormer 1.2 1.51 2.1 x

. o s. chagz e stockr P Butane-1 Mixed B43 1 Reflner ro lene.Hydroiormer bottoms, boiling range 482-527 437-554 437-554. p py (F.) at1 atm.

Total Product Yields, Wt. per cent Based onU hargte:d

nreac e 6 Monoalkylated. 8 21 2 1; 6 Dialkylliated 00.4 106. 1 Polyaylated and Bottoms 17.9 35. 1 7. 3

Total 143 154 138 Dlalkylated Product Wt. r cent f Theoretical Yield. De0 56 8 69 Prndnnhz 9 3, Boiling Ran e, "F }541-633/760 mm n? 1 56301.5592 d4 921 0.9390. Color Idgitr a fellow (ll- Weight per centAromatics by sulfonaticn lodine No. (Wijs) 0 Viscosity at F.,Centistokes 24 46.5. 52113 03 1? )Viscosity, Universal (seconds/- 215.

1 Refine)? butane-butylene stream containing 41% oleflns 2 Men: 1Contains 47. propylene.

tends to give low values in the high ranges or aromatic content.

Example 1 A sample of butylated hydroformer bottoms was prepared by thealkylation of a three moi percent solution of technical (anhydrous)toluene sulfonic acid in dimethylnaphthalenes. The solution was placedin a 5 liter, 3 neck. flask fitted 8 V I "I filtering an i'sopentanesolution thereof through an adsorptive clay.

with an efllcient mechanical stirrer, a water conmethylnapthalene, hadbeen absorbed. Beyond this point the absorption of olefins was slow.Alkylation was then stopped and when the flask contents had cooled thereaction mixture was washed carefully with dilute alkali and then withwater in order to remove the catalyst. When vacuum distillation of thedired mixture was attempted, the presence of a white crystalline solidwas noted in the distillate; some had also solidified in the condenser.This solid was a hydrated toluene sulfonic acid which had been liberatedby the decomposition of toluene sulfonic esters at the distillationtemperature. The solid was found to be very soluble in water and highlyacidic. The distillation was continued, however, at total take-oflallowing remaining esters to "decompose until the temperature reached410 F,

at 3 to 4 mm. Hg pressure. The toluene sulfonic acid was washed out ofthe distillate with dilute to an' ester derived from said olefin andaromatic sulfonic acid, the steps which comprise disconalkali andnonalkylated and unreacted hydrocarbons were removed by topping thisdistillate through a 60 x 2.5 cm. column packed with inch Fenske helicesto an overhead temperature of 450 F. at 200 mm. pressure. The productwas diluted with isopentane and decolorized by filtering through clap..Aiter solvent removal the mixed monoand di-butyl dimethylnaphthaleneyield based on crude butylated .product was 75 weight percent. Physicalproperties were determined and are listed in Table II under product 1.

Example 2 'of the exhausted gas were taken from time to time andanaylzed for total unsaturates. As alkylation progressed the reactionbecame slower --and the concentration of olefins in the exhausted gasincreased until a constant value was reached. Toluene sulfonic estersformed in the course of alkylation were removed from alkylation productsby allowing them to alkvlate more naphthalanes after the addition of theolefin charge was Example 3 Propylene from a refinery stream was-used;under conditions similar to tho'seemployed in butylene alkylation (seeExample 2) to alkylate Y .a mixture of mono-., di-, andtri-methylnaphthalene to produce dipropyl derivatives. Upon completionof alkylation, propylene injection was discontinued and the alkylationreaction mixture was maintained, with stirring, at the reactiontemperature for four hours to convert toluene sulfonic propyl esters tofree toluene sulfonic acid and additional alkylate.

then fractionated.

It will be evident that the above examples able hydrocarbon wherein saidhydrocarbon iscontacted in an alkylation zone with an added olefinstream and a substantially anhydrous aro- ,matic sulfonic acid, wherebysaid alkylatable hydrocarbon is alkylated and a'substantial proportionof said aromatic sulfonic acid is converted tinuing theaddition of saidolefin stream upon completion of the desired alkylation reaction,subjecting the alkylation reaction mixture to a temperature and for atime suflicient to efiect substantial conversion of said ester wherebyaromatic sulfonic acid is regenerated, diluting the alkyla-v tionreaction mixture with a saturated hydrocarbon'in quantity suflicientsubstantially to reduce the solubility of the aromatic sulfonic acid ini the alkylation reaction mixture, whereby the arcdiscontinued. To thisend, an "after-alkylation period of 3-4 hours was allowed, followed bycaustic washing to remove regenerated toluene sulfonic acid. The resultswere'very satisfactory,

as judged from the fact that no evidence of' toluene sulfonic acid onfinal distillation could be found. After the initial alkylation productwas treated with alkali, it was substantially neutral. However, afterthe after-alkylation" operation the product was distinctly acidic,showing that toluene sulfonic acid was liberated. The color of thealkylation products was improved by matic sulfonic acid separates as adistinct stratum from the alkylation reaction products, and recoveringaromatic sulfonic acids so produced.

2. The process of claim 1 wherein at least a portion of the aromaticsulfonic acid which is regenerated and recovered from the reactionmixture is recycled to the. alkylation zone.

8. In a process for the alkylation of an alkyl polycyclic aromatichydrocarbon wherein said hydrocarbon is contacted with an added olefinstream and a small, catalytic quantity of a substantially anhydrousaromatic sulfonic acid, whereby said alkyl polycyclic aromatichydrocarbon is alkylated and a substantial proportion of said aromaticsulfonic acid is converted to an ester derived from said olefin andaromatic sulfonic acid, the steps which comprise discontinuing theaddition of said olefin stream upon completion of the desired alkylationreaction, subjecting the alkylation reaction mixture under conditionsprecluding substantial distillation thereof to a temperature in therange of about F. to about 400 F. for a period of time between about 0.5and about 10 hours to effect substantial conversion of said ester,whereby aromatic sulfonic acid is regenerated, diluting the alkylationreaction mixture with a saturated hydrocarbon in quantity suflicientsubstantially. to reduce the solubility of the aromatic sulfonic acid inthe al- 'kylation reaction mixture, whereby the aromatic sulfonic acidseparates as a distinct stratum from the alkylation reaction productsand recycling at Regenerated toluene sulfonic acid was removed from thealkylate by washing with aqueous caustic and the alkylate was 9 least aportion of reaenerated. substantially anhydrous aromatic sulionic acidthus recovered to the alkylation operation.

4. The process of claim 1 wherein the conversion of the aromatics'ultonic ester is eflected at a temperature between about 150 1''. andabout 400 F. for a period .of time between about 0.5 and about 10 hours}5. The process of claim 1 wherein the aromatic suifonic acid issubstantially anhydrous toluene sulfonic acid.

6. The process 01 claim 1 wherein the alkylatable hydrocarbon is analkyl polycyclic aromatic hydrocarbon.

'7. The process of claim 1 wherein the alkylatable hydrocarbon iscontained in a fraction comprising a substantial proportion ofmethylnaphthalenes. said fraction boiling between about 437 1''. andabout 554 Eat one atmosphere.

8. The process of claim 1 wherein the aromatic sulionic acid issubstantially anhydrous toluene sulionic acid and wherein thealkylatable hydrocarbon is contained in a traction comprlsin: a

10 substantial proportion said traction boiling between about 437 F. andabout 554 F. at one atmosphere.

3"; ROBERT J. LEE.

REFERENCES CITED The following references are of record in the tile oithis patent:

; UNITED STATES PATENTS Number Name Date 2,014,766 Isham Sept. 17, 1985.-2,390,835 Hennion et al Dec. 11, 1945 12,390,836 Hennion et al..- Dec.11, 1945 2,409,389 Ringham Oct. 15, 1946 Lieber Nov. 26, 1948 :2,411.51aj" OTHER REFERENCES Oranic Chemistry of Sulfur," by Suter. published byJohn Wiley and Sons Inc., N. Y., 1944:

copy received in Library of Patent Oiiice, June 22, 1944: pages 525 and526.

oi methylnaphthaienes'.

